1. Field of the Invention
The present invention relates to methods and devices for applying finish to yarns in motion at high speeds of about 3000 meters per minute (m/min) or greater, and to the products formed thereby.
2. Description of the Related Art
Liquid finishes are typically complex mixtures of water, oils, polymers, and surfactants applied to yarns to achieve desired processability characteristics including lubricity and reduction of static electricity, and to improve end use properties. For some applications, such as tire cord yarns, more than one finish, is applied. A first finish is applied to facilitate drawing operations during yarn manufacture. A second finish or overfinish is applied to aid in bonding the yarn to rubber during tire construction.
The function of a finish applicator device is to apply finish at an even rate to a travelling yarn so that the filaments of the yarn are evenly coated with the finish. Conventionally, yarn finishes are applied by advancing a running yarn threadline in contact with the surface of a xe2x80x9ckiss rollxe2x80x9d rotated in a liquid reservoir containing the desired finish, or by means of applicator tips or sprays.
As used herein, xe2x80x9cactive finish applicationxe2x80x9d refers to a method by which finish is supplied to the yarn using force, such as pressure or injection. The finish may be applied by impingement of a jet under pressure or by full immersion under pressure. Active finish application is in contrast to the prior art methods which are herein termed passive wherein the finish is provided at about atmospheric pressure on a roll or applicator tip and the yarn picks up some finish as it passes through a film of finish. As used herein, pressure means the highest pressure at the finish-yarn interface along the yarn path through an applicator device.
Prior art finish applicators are described for example in U.S. Pat. No. 2,294,870 to Kline et al.; U.S. Pat. No. 3,244,142 to Walker; U.S. Pat. No. 3,754,530 to Pierce; U.S. Pat. No. 3,988,086 to Marshall et al.; U.S. Pat. No. 4,325,322 to Louch et al.; U.S. Pat. No. 4,329,750 and U.S. Pat. No. 4,397,164 to Binnersley; U.S. Pat. No. 4,526,808 to Strohmaier; U.S. Pat. Nos. 4,544,579 and 4,565,154 to Mullins et al; U.S. Pat. No. 4,851,172 to Rowan et al.; U.S. Pat. No. 4,891,960 to Shah; U.S. Pat. No. 4,984,440 to McCall; U.S. Pat. No. 5,181,400 to Hodan; U.S. Pat. Nos. 5,679,158 and 6,067,928 to Holzer, Jr. et al.; United States Statutory Invention Registration H153 to Sadler et al.; and DD 122,108 to Henssler. However, difficulties with these devices arise when yarn speeds increase to about 3000 m/min or even less. In none of these devices was there an attempt to disengage or block an air boundary layer in motion with the yarn.
A running thread line entrains a boundary layer of the fluid, air or liquid, through which it passes. The boundary layer of fluid moves at the speed of the thread line at its surface. The mechanics of boundary layers have been analyzed most notably by H. Schlichting, Boundary Layer Theory, McGraw Hill, New York, 1960 and in the context of moving continuous surfaces by B. C. Sakiadis, A.I.Ch.E. Journal, 7(1,2 and 3), 26-28, 221-225, 467-472 (1961). A thread line moving at high speed in air, when brought into contact with a liquid, creates a violent turbulence at the intersection where the air boundary layer in motion with the thread line impinges on the liquid. In the context of application of liquid finishes to high speed running yarns by conventional kiss rolls and applicators, the air boundary layer limits the concentration of finish that is applied to the yarn, causes large variation in finish pickup and creates excessive spraying of finish to surrounding areas.
Prior art attempts to resolve these problems have been described for example in U.S. Pat. Nos. 4,253,416, 4,255,472, 4,255,473 and 4,268,550 to Williiams Jr.; and U.S. Pat. Nos. 4,675,142 and 4,855,099 to D""Andolfo et al.
EP 0195 156 A2 describes spinning and applying finish to yarns at speeds of about 4000 m/min by means of spray nozzles.
The disclosures of Williams Jr. attempt to ameliorate the effect of the air boundary layer on the finish supply without actually interrupting the air boundary layer. These disclosures qualitatively describe more uniform finish application by the patented devices but no quantitative information is provided regarding the concentration of finish on the yarn or the finish uniformity.
U.S. Pat. Nos. 4,675,142 and 4,855,099 to D""Andolfo et al. apply finish to the yarn by means of opposing spray nozzles. No attempt is made in D""Andolfo et al. to influence the air boundary layer prior to finish application. Instead, the excess finish sprayed from the yarn is captured in large fixed enclosures. In U.S. Pat. No. 4,675,142 finish concentrations on the yarn up to 1.36% by weight are reported but finish concentrations varied by 15% to 35% of the average value.
In a different area, U.S. Pat. No. 5,624,715 to Gueggi et al.; U.S. Pat. No. 6,146,690 to Kustermann; and U.S. Pat. No. 6,248,407 B1 to Hess describe methods of applying a coating to a moving planar surface involving interruption of the air boundary layer in motion with the surface.
A need exists for finish applicator devices capable of actively applying finish to one or more yarns running at speeds over 3000 m/min, uniformly and at sufficient concentrations. A further need is for these devices to contain the finish and prevent spraying and contamination of surrounding areas. A yet further need is for these devices to be small, portable and easily installed at a variety of positions on a fiber processing line.
In the manufacture of yarns for in-rubber applications, such as tires belts and hoses, it is necessary to apply an overfinish to facilitate bonding of the yarn to rubber. It appears to be an invariable practice to apply the overfinish after the yarn is drawn and immediately before winding. See for example U.S. Pat. No. 5,562,988. This practice results in winding a wet yarn where the finish can pool and cause subsequent variations in rubber adhesion. A need exists for a finish applicator device that may be placed in a position between heated rolls on a yarn draw panel to permit drying the overfinish before winding.
The invention provides methods and devices to actively apply finish to one or more yarns in motion at speeds greater than about 3000 m/min, to achieve a finish application of 0.2 wt. % or more, and with a coefficient of variation of finish concentration of 10% or less. The devices are compact, portable and readily installed at a variety of positions on a fiber processing line. The devices of the invention contain the finish so that contamination of the surrounding areas is prevented.
The devices may be used to provide an overfinish to a moving yarn between heated godet rolls. The so-provided heating may be used to dry the yarn and to promote curing reactions in the finish and between the yarn and finish compounds. As used herein, xe2x80x9ccuringxe2x80x9d refers to any reaction, which may be accelerated by heat. Non-limiting examples include crosslinking reactions and polymerization reactions. Such curing reactions may serve to enhance properties of the yarn. Non-limiting examples of such enhanced properties are adhesion to rubber, fatigue resistance and cohesion.
In one embodiment, the invention is a method for applying a liquid finish to one or more running yarns at speeds greater than 3000 m/min comprising the steps of:
a) passing the yarns into a finish applicator device while substantially blocking the entry of the air boundary layers in motion with the yarns into said finish applicator device;
b) contacting the yarns with a liquid finish under pressure;
c) substantially disengaging the excess finish from the yarns; and
d) passing the yarns out of the applicator device.
In another embodiment, the invention is a method for applying a liquid finish to one or more running yarns at speeds greater than 3000 m/min comprising the steps of:
a) passing one or more running yarns into an finish applicator device;
b) substantially blocking and disengaging the air boundary layer in motion with each yarn and venting it to the exterior of said finish applicator device;
c) contacting the yarns with a liquid finish under pressure;
d) substantially disengaging the excess finish from the yarns; and
e) passing the yarns out of the applicator device.
The invention also includes a yarn manufacturing method comprising the steps of: applying a liquid finish to one or more yarns running at speeds greater than about 3000 m/min at a position between heated rolls on a draw panel; drying said finish between said rolls; and collecting a dry drawn yarn on a winder.
The invention further includes the devices utilized in the above methods. In one embodiment termed an xe2x80x9cimmersion applicatorxe2x80x9d, the invention is a device for applying a liquid finish to one or more high speed running yarns comprising an essentially box-like device having yarn entry openings constricted to substantially block entrance of the air boundary layer entrained by each yarn. The device is internally divided into two or more chambers along the yarn path connected by constricted passages. In at least one of these chambers, the yarn is contacted with finish liquid under pressure. Excess finish liquid is captured and drained from one or more succeeding chambers.
In another embodiment termed a xe2x80x9cslotted applicatorxe2x80x9d, the invention is a device for applying a finish liquid to one or more high speed running yarns utilizing an essentially box-like device having yarn entry openings and ducts behind the yarn entry openings to divert and discharge the air boundary layers at the lateral surfaces of the device. Within the device, one or more pressurized jets of finish liquid impinge on the yarns traveling in a channel. Excess finish liquid is captured and drained from one or more internal downstream chambers.
The invention also includes the finished yarn products so produced. A yarn with improved finish uniformity is provided with an overfinish actively applied and dried on the draw bench before the first winding operation. The yarn products of the invention may be used in textile and leisure fiber applications, and in industrial fiber applications, such as in tires.